1. Field of the Invention
The present invention relates to linear transmission technology and more particularly, to a circulating element for ball screw and a ball screw using the circulating element.
2. Description of the Related Art
Conventional ball screw designs commonly have a circulating element arranged in the screw nut to provide a circulating passage for enabling balls to circulate between the screw shaft and the screw nut. FIG. 1 illustrates a prior art ball screw 10, which is characterized by the formation of a mounting groove 16 in the hole wall of an axial hole 15 of a screw nut 13 for accommodating a circulating element 17, which defines therein a circulating passage 18 that is connected to an internal thread groove 14 of a screw nut 13, thus, balls 19 can move through a circulating passage that is formed of an external thread groove 12 of a screw shaft 11, an internal thread groove 14 of a screw nut 13 and the circulating passage 18 of the circulating element 17. This type of circulating element 17 can be used only under the condition that the screw nut 13 has an external thread groove located on its one end and linked to the equipment, or the internal thread groove 14 of the screw nut 13 has a short pitch, or the screw nut 13 of the ball screw has a small outer diameter. Due to the structural limitations of the screw nut, the aforesaid prior art circulating element 17 cannot be replaced by a commonly known external circulating or end plug circulating type circulating element.
However, in the aforesaid prior art ball screw 10, the mounting groove 16 of the screw nut 13 is made by electrical discharge wire-cutting technology. Except the drawback of high processing cost, the mounting groove 16 will extend through the two opposite ends of the screw nut 13 after the processing. Thus, when mounting the circulating element 17 in the mounting groove 16, it is necessary to constantly adjust the position of the circulating element 17. If position deviation occurs, connection between the circulating passage 18 and the internal thread groove 14 may be unable to achieve, resulting in an alignment problem, as shown in FIG. 2. When an alignment problem occurs, the moving smoothness of the balls 19 will be affected. If the balls 19 do not move smoothly, they will continuously impact the circulating element 17, causing circulating element damage or ball damage.
On the other hand, when loading the balls 19, the balls 19 must be loaded by lots to match the position of the circulating passage 18, i.e., load a first lot of balls 19 in the external thread groove 12, the internal thread groove 14 and the first circulating passage 18 at first, and then load a second lot of balls 19 in the external thread groove 12, the internal thread groove 14 and the second circulating passage 18, and so on, until all of the balls 19 have been loaded in every circulating passage 18. This ball loading procedure is complicated.
In conclusion, the aforesaid prior art technique has the drawbacks of high processing costs, assembly difficulty, low alignment accuracy, and poor running smoothness.